Electric heater for heavy aircraft



May 29, 1945- JL D. MORGAN'ET AL 2,377,027

ELECTRIC HEATERS` FOR HEAVY 'AIRCRAFT Filed Deb. so, 1942 lNvENoRs JOHN D. MORGAN P I ncY s. rrr av Patented May 29, 1945 ELECTRIC HEATER FOR HEAVY AIRCRAFT John D. Morgan, South Orange, and Percy B. Levitt, Millburn, N. J., assignors to Cities Service Oil Company, New York, N. Y., a corporation of Pennsylvania Application December 30, 1942, Serial No. 470,538

(Cl. 21B-39) 9 Claims.

This invention relates to improvements in electric heaters for heavy aircraft and more particulai-1y to improvements in motor oil heaters for such aircraft.

Electric heaters have been provided for heating the motor oil of ordinary aircraft in which the heater is mounted directly in the motor oil tank. However, this has been found impracticable with aircraft of the size of the American clippers which are provided with motor oil tanks holding seventyiive gallons or more. lThe installation of electric heaters directly in such large tanks have been found to be impracticable for the further reason that the tanks are bafed to avoid the pitchand roll of the oil.

These difculties have been avoided in accordance with the features of the rpresent invention by providing an electric heater mounted outside of the motor oil tank in association with means for drawing the oil from the bottom of the tank, means for conducting it in contact with the heater, and then passing it to the opposite end of the tank. The invention includes other details in arrangement of the various elements of the apparatus and in the features of the construction.

The features and advantages of the electric heating apparatus of the present invention will be apparent to those skilled in the art from the following detailed description taken in connection with the accompanying drawing which forms part of this application. In the drawing:

Fig. 1 is a longitudinal view partly in broken section of the heater assembly constructed in accordance with the present invention.

Fig. 2 is a View looking down on the apparatus shown in Fig. 1 with certain parts removed or broken away.

Fig. 3 is an enlarged detailed sectional view similar to that of Fig. 2 showing the details of construction of a portion of the apparatus shown in Figs. 1 and 2.

Fig. 4 is a cross-sectional View taken on the line 4-4 of Fig. 3, looking from the left.

-Fig. 5 is a cross-sectional view taken on the line 5-5 of Fig. 3, looking from the right,

Fig. 6 is a cross-sectional view taken on the line 6-6 of Fig. 3, looking from the right.

Fig. 7 is an enlarged vertical broken sectional view similar to that of Fig. 1 but from the opposite side showing therdetails of construction and arrangement of a portion of the apparatus.

Fig. 8 is a vertical sectional view taken on the broken line 8-8 of Fig. '7, looking from the left.

sembled apparatus in connection with a large oil tank on a heavy aeroplane.

Referring to Fig. 9 of the drawing, the general assembly of apparatus in accordance with the present invention includes an oil tank I0 of a heavy aeroplane adapted to hold seventy-five gallons or more of motor oil. The connections of the tank with the aeroplane motor and for lling and draining, are not shown. Such tanks are sometimes mounted in inclined position. The tank I0 is provided with a plurality of baiiies I2 to prevent rolling and pitching of the oil. The oil to be heated is withdrawn from the bottom of the tank at one end through a pipe I4 conducted through the electric heating apparatus of the present invention, shown generally at IE, and then passed through a. pipe I8 into the opposite end of the tank I0 at a point substantially above the bottom of the tank. The heating apparatus I6 is preferably built of light metals such as aluminum, magnesium and their alloys, and is preferably mounted in approximately the position shown with rerespect to the tank- I0 by means of the pipe connections I4 and I8. However, the heating apparatus I6, which includes an electric motor, may be held in a more rigid position with respect to the tank by means of suitable mounting brackets, not shown, which may be used to mount the appa ratus on a part of the fuselage. f

The arrangement of the electric heater,y pump, electric motor, and temperature control means is shown in Figs. l and 2, while the essential details of construction are shown in Figs. 3 to 8. The

apparatus in Figs. 1 and 2 includes a long tubular cylindrical shell 20 which houses an electric heater 22 at the inlet end and a turbine pump 24 between the end of the heater 22 and the oil outlet I8. The pump is driven by an electric motor mounted in a Water-tight explosion-proof motor housing 26 attached in alignment to a flange 28 on the left end of the shell 20.

Electric current for the heater 22 and motor is supplied from the aeroplane batteries or generator or both, or from an outside source of electricity through lead Wires 30 (Fig. 2) which terminate in a plug 32 on the side of a switch box 34. This switch box is mounted directly on the shell 20 in a duid-tight manner so that the shell constitutes the bottom of the box. A microswitch 36 is mounted inside the box directly over a bimetallic strip 38, one end of which is fastened in a fixed position to the shell 20 so that the opposite free end is directly under a switch pin 40. The switch box 34 is connected with the motor housing 26 Fig. 9 is a diagrammatic view showing the-as-' by means of a metal conduit 42 for the electric manner shown, a relatively narrow neck section Y directly over the oil inlet pipe I4, anda relatively long heating section composedoflng narrrow deep open-ended channels 52 extending from. the inlet I4 to the other endof'the heater.' It

will be noted that the seriesof`channelsextend` entirely around the casing 4B', and that the channels are separated by relatively thin parallel metal walls 54 which are integral'with the' body of the casing 4S. The casing 46 including the metal walls 54 preferably has a diameter` about alyinchsmaller thanv4 that ofA thelshell l 2U, and'isf preferably mounted so thatfth'ewalls54 do-nottouchithe shell`202 There is therefore 'artendency for 'al thin layer of relatively cool oilA to i stayV on the inside ofiv the shell' 2II-;'v.fhile1the vheated o'll flows 'througn the :channels The tubular casing` 461 isi provided with anv electrioheating unit including? ahollow cylindricalizircon core' 56 andi al resistance wire 58y wrapped therearound in; spaced convolutions throughY the length of the channeled sectionrof the heater. Theltermlnalsoffth'elresistance wirei 58. areattachedrespectively to' studs B0 mountedi ini` a: plasticl insulationt comprising-f the head1 of'. the heater 22.` Th'e resistance` wire1 58S may bef chromium, nickel chromium. alloy, .or Ialuminum cobalt-iron'. alloy.

InmakingupA the heater' 22- after thei outside machining isi completed; the'V resistance wire. 58k

and the: core 5B. are.` coated A with a Zircon washV madeof 50% ofv milled grainzirc'on. and: 504% ofA natural, grain Zircon bonded with. al mixture` ofi 6%-`P205 l ande 2% `chromic acidl. This`V coating; is' hardened" on: the'. wirei andthe core'M by heating i thisrassemblyA to: a'.temperature' of aboutv 6'0OF l inanroven; Thecore'fandfresistance'wire assem bly is mounted inuthe' metall casing 4B: in spacedrelationV to thev metal wall; theispace'. beingnlled with iine Zircon sandl621which'isialgootlldielecL tric andl atthefsamelftime hasfav high'. heatlconductivity. This.` layer; off sand.V completely surrounds tlie-V core-and resistance wire andi mayV be very" denselyv packedV by.I vibrating` the: casing as the sand. is introduced;y The'y packed-int sand is held in` place f by the: plastioinsulation head1 orV otherV suitable means'.

The t'urbine'pump 24 is shown more inf detail. in'F-igs. 3 toiand comprises animpeller 64provided with vanes- 65,- mountedtony the endl of a relatively long shaft 66 in aichamber. formedbe'- tween the oil outlet I8. andthe end ofA theheater" 2v2. Thefnlet of therchamber'comprises'the central opening in a specially shaped'annular mem'- ber'l 67', the outer circumferenceof which fits the inside of the shell 20 and is attached: thereto closely adjacenttheend of the heater 22. The back of the pump chamber, or housing` for the impeller 64, comprises an. annular cup-shapedV member' ttedfon the end of a tubular housingJ may-'be integral-'with the member 68,` or solderedv or otherwise fa'stenedtothe memberl 68.y

l 7U. insidev the. shell 20,

The impeller shaft 65 which is connected to the electric motor in the housing 26, is mounted in a bearing 14 in the right end of the tubular housing T0 and in a ball-bearing 16 mounted in the motor housing 26, the housing 'IIJ being iirrnly attached to the motor housing 26 by a hanged member 18 with an intervening packing 80 for the shaft 66. Small amounts of oil may flow through the bearing 14 along the shaft 66 when the pump is not running, but the packing will prevent lthe entry of any oil into the motor housing. A` gasket,` is also used between the flange 28 and the motor housing 26 to prevent leakage of`oil fromthespace around the shaft housing picks up the heated oil as soon as it leaves the heater 22 and throws it around the cup-shaped member SB-intothevspace to the left of the pump andforces the heated oil out through the line |8` by which it is conducted back into the tank 10i. The` arrangement of the. heater` and pump issuch: that the: pump: impellerfis practically always: operating inf the hghest temperature. oil` in the system when the heater is on; andi keeps up theV circulation throughv the: apparatus until oilin thez'tanklreaches the desired temperatura The detailedarrangementv of the eleotriclwiring and temperature control meohiamismfor" the heater and pumpmotor is shownirr detail iniFlgs:

74 and. 8A inl whichv the microswitch 35: is" shown! as being 'mounted f between positioning.r side :bearings inthe switch box 34y by means1of1 a 'xed cross-bolt 82e` and` an eccentric.'screw-bolt'A 841 ther latter of whichis providedlwith an outside. indi ,t ycator as shown in Fig, '7. The switchzSis-proi so that longitudinalzmovementmay befobtainedl when the bolt84 is turned.. 'Ilhe bolt ihispositioned directlyv overA the,- switch pin 40,1and'is. adapted when rotated to'raiseor lower the left.

end of theswitchzS (Fig. 7) withlrespect tothe free end=of thebimetallic stripw; asshown by the structure ofthe eccentric bolt.84 in `Figli.

Thelbimetallic strip :it isv mounted'rdrectlyf on pointy of mounting', is transmitted directly tothe bimetallic strip.A When the oil.` beoomessutliciently hotfin the tanlcthefreef end` oi` thastripy movesV up; engagesthe.` pin 407 and eventually forces-thev pin-.up and throwstheswitchfto cutofli the supply of'` current tothe electric heaterl The motor. and pump is.` kept runningoontinuousiy to-keep the temperature.A uniform :in the' tank; l

In accordancewith' the wiringi arrangement shownA in Fig. '7, a lead wire-as-runsdirectly Imm the plug=32to one-of thefstuds fwhile afbranch wire leads from the wire 88 throughsthe nous ing 341and conduit 42 to' thefelectric motor. A second wire 92 fromrthefplugiil` leads to anattachment'on'the switch 35- whilefa# Wire? desde from a second attachment on theswitch Noto the: second stud. 60./ A wire 96 is connected to the wire 92 or its'swivtonattachment andzlelds through the conduit y42m therelectricvmotor, so

that themotor. isv connected in as--soon as: the:

plug 321s connected to a currentlsupplyf Enom theforegoing description and'arrangement ofl the The turbine pump 24 asfor example when the plane is at'its base. The pump keeps the oil temperature uniform while the heater gives the desired temperature. vWhile the shell has been shown and described as cylindrical and the shape of the other elements mounted therein described as of the same cross-section, it is to be understood that a different cross-section may be used such as rectangular, elliptical, etc. Furthermore, while the turbine pump shown and described is the preferred form and particularly adapted for the purpose, it is to be understood that a pump oi other structure may be employed for circulating the oil from the oil tank through the heater and back into and through the tank. Various other modifications may be made in the details of construction and arrangement without departingy from the spirit and scope of the invention.

In the handling of the aeroplane motor oil in accordance with the present invention, the indicator on the screw-bolt 84 is preferably set so that the switch pin 4B is thrown to cut oi the current at the temperature desired for the oil in tank l0. In some cases, this temperature may be relatively low such as zero degrees or 10 F., especially where aircraft is not operated under emergency conditions. A setting of the indicator to maintain this temperature will prevent freezing of the motor oil and will keep it sufficiently fluid for ordinary use. gency conditions, it may be desirable to maintain the oil in the tank l0 at a relatively highv temperature of from 100 to 200 F., so that the aircraft can take oif on a few minutes notice without waiting for the usual rather long period for warming up the motors. A temperature of 150 F. may be suitable for a quick take-off, butif the motors are cold, it may be advisable to heat the oil in the tank I0 (and other tanks) to a temperature as high as 250 F. and maintain it at that temperature during an emergency so that once the motors are started the extra heat in the oil will aid in warming up the motors quickly. (In most cases there is a separate tank for each other.)

Regardless of the temperature at which the oil is maintained in the tank l0, the tank is preferably insulated against heat loss as are also the lines M, I8 and the shell I8, including the switch box 34. The film of oil on the wall of the shell I0 is of some help in preventing loss of heat. The scale opposite the indicator bolt 84 may be calibrated so that it will be possible to tell at a glance the temperature for which the indicator is set. While in accordance with the preferred form of the invention the apparatus has been described in connection with the motor oil tanks of aircraft, it is to be understood that the apparatus may be advantageously used on internal combustion engines of various kinds for keeping the crank case oil at the desired working temperature or for keeping cooling water or other cooling fluid at a working or other predetermined temperature, such as for example to prevent freezing.

Having described the invention in its preferred form, what is claimed as new is:

1. An apparatus for heating the motor oil of a heavy aircraft, comprising a tank for the oil, an oil outlet pipe leading from the lower portion of the tank and connected into the side of a relatively long vertically 'mounted tubular shell near one end thereof, said shell containing an electric heater and a turbine pump, an oil return pipe leading from the opposite end However, under emerof said shell T5 and connected into the tank at a point remote from said oil outlet pipe, said heater being mounted in said shell near the oil inlet thereto and adapted to heat the oil rto a predetermined temperature, said pump being mounted in said shell between said electric heater and the inlet to said return pipe and adapted to draw oil from said tank through said heater and force the resulting heatedy oil back into said tank through said return pipe, an electric motor mounted on top of said shell 'and connected for operating said pump, means for supplying electric current to said motor and heater from a common source, a switch in the current line to the heater, and control means responsive to changes in the temperature of the oil inl the` apparatus connected to said switch in such a way as to cut olf electric current to said heater when the oil reaches a predetermined temperature without cutting o the electric current to said motor.

2. In an apparatus for electrically heating motor crank case oils and for keeping such oils at the desired working temperature including a container'for the motor oil and an electric heater for heating the oil, an oil outlet pipe leading from the lower portion of the container and connected into the side of a relatively `long tubular shell near one end thereof, said shell containing said elec`- tric-heater and a pump, an oil return pipe leading from the opposite end of said shell and con'- nected into said container at a point remotefrom said oil outlet pipe, said heater being mounted in said shell near the oil inlet thereto, said pump being mounted in said shell between said electric heater and the inlet to saidreturn pipe andl adapted to draw oil from said container over saidy heater and force the resulting heated oilback Into said container through said return pipe, an electric motor for driving said pump, a common source of electricity forsaid motor and said electric heater, and control means resposive to changes in the temperature of the oil in said shell near the oil inlet connected to cut 01T the electricity'to said heater when the oil reaches a predetermined temperature Without cutting` ofi' the electricity to said electric motor.r

3. In an apparatus for electrically heating motor crank case oils and for keeping such oils at the desired working temperature including a container for the motor oil and an electric heater for heating the oil, a pipe leading lfrom the lower portion of the container and connected into the side of a relatively long tubular metal shell near one end thereof, said .shell containing the electric heater, an oil return pipe leading from the opposite end of said shell and connected into said container at a point remote from the inlet of said iirstunentioned pipe, said heater being mounted in said shell near the oil inlet and adapted to heat the oil to the desired working temperature, a pump mounted in said shell between said electric heater and the inlet to said return pipe, said pump being adapted to draw oil from said container over said heater and force the resulting heated oil through said return pipe into said container, means including a switch for supplying electric current to said heater, and control means responsive to changes in the temperature of the oil in said shell near the oil inlet connected in such a way as to operate said switch and cut off the electricity to said heater when the oil in the container reaches said working temperature.

4. In an apparatus for electrically heating motor crank case oils and for keeping such oils at the desired working temperature including a. containerfor the.v motor oil and an electric. heater forheatingfthe'oil; a pipefleading from: the; lower portion-.0f` the. container and; connected into. the side: of a relatively loing vertically` mounted shelly near, oneend. thereof, saldi shell containing the. electric heater, anioil returnpipe.- leading( from.4 thef opposite` end` ofsaid. shell and; connected into said. container ata point: rerniote.A from said mst-mentioned pipe. said-v heaterf bee ingmounted in saidshell in spacedrelation there-A from near. the oi1 inlet. andN adapted: to'- heat. the oil tothe; desired working.V temperature; a pump mountedl in said. apparatus.- adapted: to:- circulate oiLfromisaid container. through. said heater.' and; through said .returnV pipe backfto. said'. container; an electric motor` for driving saidygiunna,.aicomfv mon source: of electricity; for. said; motor and heater, andsmeans responsiverto changes inf the temperature of: the.y oily in said; shell near the oilV inlet connected in Suche azwayasztoucut off-'the electricity to said heaterwhenthe-oil inithelcontainer reaches said working. temperature Without cutting oil the, electricity to saidmotor.

5'. An apparatus. as denedlby claim.4 inwhich said. heater includes acasing containingexteriorf longitudinal oil-heating channels.

6. In anapparatus for 'electrically heatingmotor crank case oilsandfor; keeping suchoilsaty the desired. workingl temperature` includingV a. con tainerforvthe motor oil andan electric heater for heating the oil, a pipe leading fromthelower' portion of thecontainer. and connected into the' side of a relativelyI longvertically mountedshell near onelendfthereosaid shell. containing thel electric heater, an oil; returnpipei leading from the. opposite endof saidzshellandf connected into said. container at a point' remote. fromlsaidnrstmentioned. pipe, said heater; being. mounted` in said shell near the-oiliinletandzadaptedrto heat the oil to the-desired working; temperature, a turbine pump mounted inv saidshell. betweenv saidy electric heater and. therinlet: to. said. return-.pipa said pumpbeing` drivenby an electriczmotor and adapted to draw oil fromsaichcontainer oversaidf heater. a.nd.force theresultingheatedioil through said return. pipe into. said container-4.a'. common sourceof electricty .for saidizmotor.` and heater, and meansv responsivev to. changes.'` in: the tem'e puatuxfaoithe oil'insaid shell near theol) inlet.

connectedixrsucha way acto cut or! the=elec tricity` to. saidiheater when thev oil. in the ccn-v tainer. reaches said workingtemperature without cuttingoil; the; electricityl to said motor.

7. An apparatus as denedby claim 6 in which. saldiI heater.'` comprises a` casing. havingv an end less series; of. longitudinal oil-heating. passages and: is spaced'slightly from said shell.

8f. An apparatus.- for heating the-motor oil of:

a` heavy aircraft, comprising a tank. for the. oil, an oil outletnine leading from the lowei portion ofrthetanlc and connected into theside of-a rela,-4 tively.f long tubular. metal shell near one. end; thereon, saidrv shell containing; an electric: heater and apump; an-oil return pipeleadingv fromfthe. `opposite-endofsaid shell and .connected intothe tank at afpoint. remote from-said oil outletzpipe, said heater. beingpmountedin said shellnein` the oilf inlet .thereto and adaptedtaheatthe-oillto apredetermined temperature; saidv pump being mounted-1in. said shell between said electric heater and the inlet to said return pipe: and adaptedto draw oilifronr said. tank through said heater. and. forcefthe-resulting heated oil back-.intosaidftankf through' said., returnv pipe,` an electric; motor mounted at thev pump end of saidshelltandcon.- nected for. operatingV said pump, means for supplying.; electric current tosaid motor and heater fromi'a common source, a. switch-inv the currentA line. to :the: heater,- and control meansiresponsive to:- changes in the, temperature: of theloil inthe'- apparatusl including a., bimetallic strip fixed to saidf metalshell: tov receive heat therefrom and mountedin-operative;relation to said switchand armngedtocutoirelectric currentto said heater whenvthe.` oil.- reaches f a. predetermined tempera-- ture without cutting-olf the electric. current tok JOI-IND. MORGAN. PERCY B( LEVI'IT. 

